1. Field of the Invention
The present invention relates to an ink jet printer, and relates more particularly to an ink priming method therefor, and to an ink jet head recovery process applied after ink priming.
2. Description of the Related Art
Once a user purchases an ink jet printer and installs an ink cartridge into the printer in order to use it, an ink priming operation is required to charge the ink path from the cartridge to the nozzles with ink from the ink cartridge. Methods accomplishing this with an ink suction mechanism have been proposed. Japanese Unexamined Patent Application Publication (kokai) 8-267785, for example, teaches an ink jet printer comprising such an ink suction mechanism.
Immediately after priming the nozzles of the print head by filling the ink path with ink from the ink cartridge, a large number of air bubbles is left in the ink path due to the ink passing a filter disposed in the ink path. The bubbles also tend to accumulate where there is an offset in the walls of the ink path, such as that part of the ink path where the ink supply tube connects to the head. While the bubbles are sufficiently small, the bubbles become trapped in the corners of these offsets and are thus not in the path of ink flow produced by suction in the ink recovery process. These small bubbles thus do not reach the nozzles, and therefore do not cause nozzle failure, that is, ink ejection problems.
Small bubbles that are trapped in these offsets gradually grow as a result of, for example, a rise in ink temperature after the printer power is turned on, and an increase in surface tension resulting from aggregation of numerous small bubbles. Eventually the bubbles grow to a size at which the bubble B protrudes from the offset and is affected by the flow of ink through the ink path. As shown FIG. 12, the bubble B may block the ink path. A bubble large enough to protrude from the ink path offset into the ink path can then be pulled into an ink chamber in the print head at the flow rate produced by a normal suction type ink head recovery process, but will not be expelled from the nozzle.
Small bubbles trapped at such offsets in the ink path immediately after the ink priming operation also cannot be expelled from the nozzles no matter how much the ink flow rate is increased for the head suction recovery process.
Bubbles that become attached to an inside wall of the ink path during the ink priming operation and there remain are also gradually freed from the wall into the ink path as surface tension increases and the wetness of the inside walls increase over time. As a result, these bubbles are carried toward the ink head and are left in the ink nozzle(s) by the ink suction operation used for regular head recovery. When the head is then driven for printing, bubbles in the nozzles cause such printing problems as non-firing nozzles.
The size of small bubbles formed by ink priming also gradually increases as a result of an increase in printer temperature when the ink jet printer power is left on. Temperature rises approximately 10 degrees in the first hour after ink jet printer power is turned on, and continues to gradually rise thereafter. Some conventional ink jet printers therefore run the head recovery suction process immediately following ink priming in an attempt to remove these small bubbles, but this results in wasted ink consumption.
When the bubble size grows to a point at which it affects ink flow after ink priming, some conventional ink jet printers apply a normal nozzle recovery suction process using a small amount of ink. With this method, however, bubbles are conversely transported into the print head pressure chamber. As a result, driving the diaphragm to pressurize the chamber simply compresses the large bubble (Pascal""s law); pressure is therefore not transmitted to the ink, and ink cannot be ejected from the nozzles.
Therefore, it is an object of the present invention to overcome the aforementioned problems.
With consideration for the above problems, an object of the present invention is to provide an ink jet printer and an ink head recovery process therefor wherein ink waste accompanying an ink suction head recovery process can be reliably avoided, and ink ejection defects accompanying a nozzle recovery suction process as a result of bubbles left in the ink path during ink priming can be reliably avoided.
To achieve these and other objects, an ink jet printer according to the present invention comprises a print head having ink nozzles for ejecting ink droplets; an ink tank for storing ink; an ink path for supplying ink from the ink tank to the print head; and an ink suction unit having at least an ink pump and a nozzle capping member for suctioning ink from the ink nozzle. The ink suction unit also performs a post-priming head recovery process for further suctioning ink after ink is first filled from the ink tank to the print head by way of the ink path.
A further ink jet printer according to the present invention has an ink tank for storing ink; an ink jet head for expelling ink from a nozzle for printing a character on a printing medium; an ink path to which ink is supplied from the ink tank for supply to the ink jet head; and an ink suction unit for suctioning ink from the ink nozzle by way of a nozzle cap for initially filling the ink path from the ink tank to the nozzle. The ink suction unit suctions a specific amount of ink from the nozzle after a bubble left in the ink path during ink priming grows to a particular size.
The ink suction unit preferably comprises at least a nozzle cap for covering the nozzles, and an ink suction pump connected to the nozzle cap.
An ink priming method for the print head of an ink jet printer according to the present invention comprises: an ink priming step for first charging ink to an ink path for supplying ink to an ink nozzle of the print head; a step for determining whether a specific time period has elapsed since the ink priming step; a step for performing a post-priming head recovery process wherein ink is suctioned and expelled from an ink nozzle when the specific time period has elapsed.
An ink jet printer and ink priming method according to the present invention can thus reliably expel from the ink nozzles small bubbles that are formed during the ink priming process and later grow to bubbles of a certain larger size.
The post-priming head recovery process is preferably performed after a specific time period elapses following ink priming. When this post-priming head recovery process is performed after waiting a specific period of time, bubbles that are formed during ink priming, accumulate in offsets in the ink path where the ink path diameter changes, have grown to a certain size, and are free in the ink flow can be reliably expelled from the ink nozzles. As a result, waste from ink suction accompanying a head recovery process can be prevented.
The post-priming head recovery process also suctions a larger volume of ink than does a normal head recovery process. Bubbles that remain in the ink path after ink priming can thus be reliably expelled from the ink nozzles and prevented from stopping in the pressure chamber. Printing defects attributable to a head recovery process can therefore be avoided.